Power hammer



Dec. 18, 1951 c. A. HlRscl-IBERG POWER HAMMER Filed April 14, 1949 f. my T5 wilg MM Mm WS .7 1%

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L. .1. $70 9N i/ M4 wud A 7J n w w Patented Dec. 18, 1951 UNITED STATES vPATENT OFFICE POWER HAMMER Charles A. Hirschberg, Mountain Lakes, N. J Application April 14, 1949, Serial No.187,3'78

(Cl. 12S-7) cushion with an inner, crank connected piston.

Important objects of the present invention are to assure a proper air couplingibetween the pistons, whenv required to effect the cyclic operation ofthe machine, and to prevent this air coupling from interfering withor impairing the striking power of the outer piston.

Related objects are to provide simple and practical mechanism for automatically and effectively providing the necessary air coupling as such and for releasing this coupling and dissipating its cushioning effect on the power impulsestroke of the machine.

- Special objects of the invention are. to effect reductions in the weight and sizeof such `Inachines, rendering them more suitable for port-v able, hand operation. f

-f Other desirable objects attained by` the invention will appear or are set forth in the following specification, broadly defining and lclaiming the invention.

` The drawings accompanying and forming part of the specification illustrate certain present practical embodiments of the invention. Structure and arrangement of parts, however, maybe further modified and changed as regards the immediate illustration, all within .the true intent ofthe invention, as will appear from the breadth and scope of the following specification and claims.

Fig. 1 in the drawings is a vertical sectional viewof the 'power hammer showing the pistons at top stroke andthe drill rod indicated broken away;

Fig. 2 is an enlarged transverse sectional view across the plane of the intake and exhaust ports on substantially the line 2 2 of Fig. 1;

Fig. 3 is a broken vertical sectional view on a plane at right angles to that of Fig. 1;

Fig. 4 is an enlarged broken transverse sectional view through the compression chamber at the lower end of the working cylinder, on sub-V molaims.

secting the choker and air inlet valve and the fuel injection nozzle;

Figs.Y 5, 6 and 7 are broken sectional and some what diagrammatic views illustrating successive positions of the outer and inner pistons.

In the machine illustrated the working cylin-v the machine as a two-cycle internal combustion enginev and to provide, as needed, an air coupling cushion between the two pistons.

. The outer, elongated piston Il is shown ashaving a rhead It at the upper end cooperative with the cylinder head Il to provide a combustion chamber, and a head I8 cooperative with the lower end I9 of the cylinder to form an air induction and mixture compression chamber and engageable with the anvil 29 to apply the striking force to the drill steel or other tool element 2|.

The crankshaft I5 is shown journaled in position extending transversely and diametrically across the mid-length portion of the working cylinder and the long, outer piston is shown slotted at 22 in opposite sides to pass the crankshaft and in turn to be guided thereby.

Additionally, the outer piston is shown slotted at 23 in opposite sides in a plane at right angles to slots 22 to provide clearance for rotation of the crank and lower connecting rod bearing. Thisenables construction of the Working cylinder in substantially cylindrical form and practically all of the same diameter.

The machine may be operated as a simple internal combustion engine with carburetor or fuel injection' orv on the diesel or other approved cycle.v

In the present illustration, air is taken into the compression chamber 24 through inlet ports 25 on the up-stroke of the lower piston head I8, fuel introduced through a lower :port 255 by injection nozzle 2l, and the mixture compressed on the down-stroke of the piston and passed by transfer passage 28 to the intake ports 29, Figs. 1 and 2.

The intake of air into the lower compression chamber 24 is shown controlled by'a check valve inthe form of a flat disc 39, loosely confined by a cage 3|, Figs. 3 and 4, and arranged to close outwardly against kan annular Valve seat 32 in the air intake throat 33.

An externally controlled choke Valve 34 is shown pivotally adjustable in the air intake 33,

which may be set and adjusted by a quadrant lever or the like.

The intermediate crankcase portion of the working cylinder and interior of the outer piston are shown as open to atmosphere through a breather 35, Fig. 1. The air coupling and cushion between the two pistons is created, released and restored in the present disclosure, through porting connections between the pistons and working cylinder.

Specifically the inner piston I2 is shown as having a port 36 extending from the top, out through the side of the same and a port 31 below the top extending from inside, out through theV skirt portion of this piston.

The outer piston is shown as having two generally similarly spaced ports 38, 39, therethrough to register at times with the inner cylinder ports 36, 31, at the inside, and with an elongated channel 40 in the cylinder wall at the outside.

This porting arrangement is such that at and about the end of the up-stroke, as shown in Fig. 5, the ports of the inner piston will lap those of the outer piston so that air conned inthe air cushion space 4I between the top of the inner piston and inside of the upper piston will be fully compressed and provide the coupling necessary for enabling the outer piston to compress the combustible mixture in the combustion chamber 42 between the head of the outer piston and cylinder head I1.

This closed, staggered relation of ports continues for a time sumcient to permit transmission of proper impulse to the inner, engine forming piston I2 and the latter, accelerating under this impulse and expansion of air compressed in chamber 4I, then carries ports 36 and 31 into registry with ports 38 and 39 at a time when the latter, in the outer piston I I, Fig. 6, are open to elongated channel 43 inthe cylinder wall, thus to relieve the cushioning air to the inside of the pistons and the crankcase. The latter, being at atmospheric pressure, through breather 35, permits reduction of the air coupling cushion to atmospheric pressure and such registration of ports continues for sufficient time to dissipate the air cushion to such an extent as not to impair or reduce the striking force of the outer piston on the tool.

Due to impact with the tool, the outer piston has a shorter stroke than the inner, crank controlled piston and this, together with the factor of acceleration of the inner piston, assures nonimpairment of the working stroke by any air cushion between the pistons.

`At and about the moment of impact, due to higher speed of the inner piston, a partial vacuum may be created in the cushion chamber 4I between the pistons, with the inner piston thus actually assisting the outer piston in striking effect.

On return stroke of the two pistons, any partial vacuum created between the pistons will assist in restoring the air cushion at 4I as soon as the ports 33, 31, in the inner piston approach registration with ports 33, 39, in the outer piston and the latter come into registration with the cylinderchannel 40, as will be understood from Aconsideration of Fig. 7. Air then trapped in chamber 4I between the two pistons constitutes the cushion for preventing rnetal-to-metal contact` between the pistons and communicating the force necessary for compression of the mixture in the combustion chamber. i

Acceleration resulting from rebound. of` the free piston also may assist in creating the partial vacuum between the pistons required to replenish the air cushion coupling between the pistons.

As a result of the construction and arrangement described, an air cushion is provided which at the moment of explosion prevents metal-tometal contact between the free piston and the crank controlled piston. Acceleration of the inner, crank connected longer stroke piston resulting partly from expansion of this highly compressed air cushion, causes the inner piston to lead the outer piston, resulting in alignment of the piston ports at a time when these ports are in register with the channel 40 in the cylinder, with consequent release of the cushioning air from chamber 4I into the crankcase, Fig. 6. Discharge of the conned air cushion enables the outer piston to strike an accelerated blow on the tool or other part, possibly assisted by tendency of the leading piston to create partial vacuum between the pistons at this time. f

This automatic release of the air cushion prior to impact enables the free piston to apply maximum'force. As the piston ports register with each other and with the channel in the cylinder wall, air from the crankcase at atmospheric pressure, pos'- sibly assisted by partial vacuum created between the pistons, enters the cushion chamber 4I, thus automatically restoring the air coupling between these pistons and enabling the inner piston under compulsion of the crank,` to carry the outer, free piston to the full topof the compression stroke, as in Fig. 5.

This automatic release and restoration of the air cushion'andlcoupling is of advantage in facilitating internal cooling and lubrication of thev parts. The breather 35, while opening the crankcase portion of the machine to atmosphere, may be designed to prevent escape of lubricant so that all internal parts can be properly lubricated. The lower or inner end of the free piston, in addition to forming a hammer, operates with air pump eifect to draw air into compression chamber 24 and to compress such air mixed with fuel injected by nozzle 21 and transfer the com'- bustible mixture through passage 28 to intake port 29. Passage 28 may be formed as a channel cored in the wall of the cylinder, as indicated inA Fig. 1.

To eect the pumping operation described and to perform necessary intake and exhaust valve functions, the outer, free piston shouldbe ,assured full stroke operation even in the event of ignition failure.

Accordingly, a piston follower may be provided, as illustrated in Figs. 5 6 and '7, and embodying in this case a tubular plunger 43 operating through the cylinder head in 4a guide 44 andA bearing at its inner end on the head of the free piston under pressure of an enclosed spring fr45. A bleeder hole 46 is shown in the side of the tubular guide 44 to release air trapped in the tubular follower, and this relief opening may be located so as to be controlled by the plunger 43, as indicated in Figs. 5 and 6, for holding a certain amount of trapped 'air as an air cushion assisting operation of the follower springll5.A

The piston follower construction-isnot shown in Figs. 1 and 3, but it will vbe'appreciated that when employed it may be centrally located, as shownin Figs. 5, 6 and 7, and the spark plug 41, Figs. l and 3, be located to one side instead of at the center of the cylinder head.

In addition to preventing `shortjstroking 7- ing connections between said pistons and working cylinder cooperative to provide a cushion ofzair between said pistons on the out-stroke of the same and to release cushioning air between the pistonsl on the inward, power stroke of said pistons, the innerpiston having a head and skirt and said portingconnections including a port opening Adown through the head and out through thev side=of the inner piston,y a port extending through the skirt of said inner fpiston, through portsv in the wall of the outer piston to lregister withsaid ports the inner piston and a longitudinal channel in the wall of thecylinder of a length to bridge the space between the ports in the outer piston and disposed to accomplish such bridging action at a part-stroke position of said pistons. v

- 6. A power hammer of the internal combustion type comprising a working cylinder, a free piston operatingv therein, a crank controlled piston operating in said free piston and porting connectionsbetween said pistons and working cylinder for vautomatically creating an air coupling and cushion between said pistons in onerphase of the engine cycle and for releasing cushioning air between the pistons in the power stroke phase of the engine cycle, including a longitudinal channel in therworking cylinder located at a partstroke position of the pistons, longitudinally separated ports through the outer piston spaced to be vconnected by said channel, longitudinally separated ports in the inner piston spaced to register with the spaced ports of the outer piston andthe working cylinder including a crankcase portion `open to atmosphere and in communication with said porting connections.

7. A power hammer of the internal combustion type comprising a working cylinder, a free piston operating therein, a crank controlled piston operating in said free piston and porting connections between said pistons and working cylinder for automatically creating an air coupling and cushion between said pistons in one phase of the engine cycle and for releasing cushioning air between the pistons in the power stroke phase of the engine cycle, including a longitudinal channel in the working cylinder located at a partstroke position of the pistons, longitudinally spaced ports through the outer piston, spaced to be connected by said channel during a predetermined portion of the stroke of said piston, and ports in the side of the inner piston to register with said ports in the outer piston, one of said inner piston ports being open to space between the two pistons for containing the cushioning air.

8.y A power hammer of the internal combustion type4 comprising a working cylinder, a free piston operating therein, a crank controlled piston operating in said free piston and vporting connections between said pistons and working cylinder for automatically creating an air coupling and cushion between said pistons in one phase of the `engine cycle and for releasing cushioning air between the pistons in the power strokephase of the engine cycle, said working cylinder having intake and exhaust ports controlled by said outer piston and a spring follower acting onvsaid outer pistonto enforce full'port opening movementof the same.

9; .Apower hammer ofthe internal combustion type comprising a working cylinder, a free pistonoperating therein, a crank controlled piston operating in said free piston and porting connections 'between said pistons and working cylinder for automatically creating an air coupling andcushionbetween said pistons in one phase of the engine cyclel and `for'releasing cushioning air between the p istons in the power stroke phase of the-engine cycle, said working cylinder having -a crankcase portion open to atmosphere and said porting' y connections being open to said crankcase portion of the cylinder and including longitudinally separated ports in both pistons spaced to register'in a part-stroke position of the pistons and a connecting channel in the working cylinder of greater length than the spacing of said ports. 10. A power hammer of the internal combustion type comprising a working cylinder, a free piston operating therein, a crank controlled piston operating in said free piston and porting connections between said pistons and working cylinder `for automatically creating an air coupling and cushion between said pistons in one phase of the engine cycle and for releasing cushioning air between the pistons in the power stroke phase of the engine cycle, said working cylinder having a. combustion chamber at one end and a -compression chamber at theopposite end, the outer piston having piston heads operative in said chambers, the compression chamber having an air inlet and a transfer passage extending from said compressionchamber to said combustion chamber and controlled at said latter chamber by said outer piston` and said porting connections including longitudinally separated ports in said pistons spaced to register in a part-stroke position of the pistons, one pair of said registering ports communicating with the space between thev ports in said part-stroke position of the pistons.y

CHARLES A. HIRSCHBERG.

REFERENCES CITED The following references are of record in the iile of this patent:

y UNITED STATES PATENTS Numb er 4 Name Date Y 1,058,268` Scott Apr. 8, 1913 2,545,999

Hirschberg Mar. 20, 1951 

